Time：2019.11.28 Source：Roller Bearings Suppliers
What is needle roller bearing？
The needle roller bearing is a roller bearing with a cylindrical roller. Relative to its diameter, the roller is thin and long. This roller is called a needle roller. Despite its small cross-section, the needle roller bearing still has a high load-bearing capacity. The needle roller bearing is equipped with thin and long rollers. Therefore, the radial structure is compact. When the inner diameter size and load capacity are the same as those of types of bearings, the outer diameter is the smallest, which is especially suitable for the bearing results with limited radial installation size. So, when choosing a needle roller bearing, you need to understand the performance in detail.
1. Carrying capacity
Generally, under the same external dimensions, the bearing capacity of the needle roller bearing is 1.5-3 times that of ball bearing, so when a large load or impact load is applied, roller bearing can be selected preferentially.
However, when the diameter is less than or equal to 20mm, the bearing capacity of the two is similar, and the price of ball bearings is lower than roller bearings, so ball bearings are preferred.
2. The speed cannot exceed the limit speed
An excessive rotation speed of the rolling bearing will increase the temperature between the friction surfaces, resulting in high heat. In this case, the lubrication of the two metal surfaces fails, and the rolling elements will be damaged by gluing.
When designing, if the rotational speed of the rotating shaft is known, when selecting a rolling bearing, we must make the limiting speed more excellent than the rotational speed of the shaft, so that the rolling bearing is safe.
3.The allowable range of angular deviation
Due to the installation error of the bearing or the deformation of the shaft, the centerline of inner and outer rings will be relatively inclined. The angle of inclination is called angular deviation. If the angular difference is too significant, it can even affect the regular operation of the shaft. At this time, you can choose a spherical bearing, such as a spherical ball bearing or a spherical roller bearing. The self-aligning bearing outer ring raceway is a spherical surface centered on the bearing center, so it can automatically align itself. Thrust ball bearings and needle roller bearings do not allow angular deviations. Thrust ball bearings can only support axial loads, and the load line of action must coincide with the axis. If there is an angular deviation, the thrust ball bearing will be severely damaged. The rolling body of the needle roller bearing is in line contact with the outer ring and is most sensitive to the axis deviation. It should be avoided when the axis is skewed.
4. Angular contact radial bearings must exist in pairs and cannot live alone.
Here angular contact radial bearings generally refer to tapered needle roller bearings and angular contact ball bearings. When the shaft is in contact with the taking, when the angular contact radial bearing is subjected to radial load, due to the existence of the contact angle, the additional axial force will be generated, so it is generally used in pairs. There are two ways to install: front and reverse. The front side is opposite the narrow sides of the outer ring, and the opposite side is opposite the full sides of the outer ring.
The rolling bearing lubricant may be grease, lubricating oil, or solid lubricant. In general, rolling bearings are lubricated with grease. Grease lubrication is not natural to lose, so it is easy to seal and maintain, and it can run for a long time with a single filling of grease. The advantage of oil lubrication is that it has less friction resistance than grease lubrication and can dissipate heat. It is mainly used for bearings with high speed or high operating temperatures.